Deep Bloober Sea is an underwater-based board in Mario Party 3. Deep Bloober Sea's name is a reference to the original name of Bloopers and is a pun on the phrase "deep blue sea". The gameboard is inhabited by (as the name implies) Bloopers as well as Cheep-Cheeps and other sea life. There are a few junctions here, but the main one is looked over by a Sushi in a submarine. Every time players get here, the shark makes them press one of four buttons before taking the path they chose. Three buttons do nothing, allowing safe passage, but one fires a torpedo at the player, blasting them to the opposite path. Additionally, the buttons do not reset until the incorrect one is chosen.

Landing on a Happening Space near the giant Blooper Baby makes it call for its mother, whose huge tentacle takes the player to the other side of the board. Action Time happens when someone lands on a Happening Space next to a giant vacuum angler fish. The arrow on the angler fish spins around, then points to the bottom, the front, or the right. Then, the angler fish starts inhaling all players in front of it. Players need to tap the A button to swim against the suction. Anyone who fails is sucked into the angler fish, then spat out in the direction the arrow points to, landing near a Sushi, Boo, or back at the start.

In Story Mode, the human player must to go up against three opponents to get the Kindness Star Stamp.